Circuit breaker arcing contact construction



Feb. 6, 1962 G. D. TOOTELIAN 3,020,374

CIRCUIT BREAKER moms CONTACT CONSTRUCTION Filed July 2, 1959 Kw f NV ENTOR.

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. 1 4504 50. morn/4M 3,020,374 CIRCUIT BREAKER ARUING CUNTACTCONSTRUCTION George I). Tootelian, Brooinall, Pa., assi'gnor to I-T-ECircuit Breaker tlornpany, Philadelphia, he, a corporation ofPennsylvania Filed July 2, 1959, Ser. No. 824,583 8 filaims. (Cl.200-146) My invention relates to an arcing. contact construction whereinthe arcing current sets up a magnetic flux to drive the arcing contactinto engagement with respect to its cooperating contacts and counteractsthe normal blow-cit forces tending to open the arcing contact.

In the circuit breakers of the type set forth in US. Patent No.2,891,123, issued June16,-1959, entitled High Speed Circuit Breaker inthe name of Chailiss I. Clausing and assigned to the assignee of thepresent invention, the movable contact is normally constructed of a mainmovable contact electrically connected in parallel with an arcingcontact. The movable contact arm is normally controlled and constructedso that when the circuit breaker is operated to its engaged position,the main movable contact will first disengage with a current pathremaining in parallel therewith which includes the arcing contact.Therefore, there is no arc drawn to the main movable contact. As thedisengaging operation continues, the arcing contact finally moves awayfrom its cooperating contact and an arc is then drawn to the arcingcontact which is specifically constructed to withstand arcing duty.

During closing, the arcing contact will normally close the circuit firstand is followed by the movable contact. Therefore, when the movable maincontact closes, the circuit has already been completed and the mainmovable contact is subjected to very little closing duty.

States Patent 3,.GZ9,374 Patented Feb. 6, 1962 ice tobias the arcingcontact in a direction to oppose blowoff force.

Accordingly, a primary object of my invention is to provide a novelstructure for opposing the blow-off force applied to an arcing contact.

Another object of my invention is to do away with the necessity ofpowerful springs for biasing an arcing contact toward its engagedposition. A further object of my invention is to utilize the biasingspring of an arcing contact as a solenoid winding for moving an arcingcontact in a direction against the blow- During the opening operation,it is desirable to have the main movablecontact open to a substantialdistance before the arcing contact opens. However, there is asubstantial blow-off force exerted upon the arcing contact whichnormally is pivotallymounted on the movable contact structure carryingboth the main movable con tact and the arcing contact. These blow-offforces can, in a circuit breaker carrying large load currents and whichare subjected to large short circuit currents reach sizable magnitudesof force and exert a considerable opening force on the pivotally mountedarcing contact be fore the movable contact has reached a sufficientlyopen position. For this reason, the arcing contact is backedup withlarge springs which normally bias toward the contact engaged position.When, however, the blow-oil? force in a particular circuit is largeenough, it is not feasible to provide biasing springs large enough towithstand the bloW-ofi force.

I have discovered that I can utilize the energy of the arcing current tohelp withstand the blow-oil force by causing this current to operate asolenoid carried by the movable contact and which includes a magneticmember connected to the pivotally mounted arcing contact. If desired,the normally used biasing spring may be connected to act as anelectrical winding or an auxiliary'means may be provided. Thus; I canutilize a biasingspring which is of a relatively high conductivitymaterial and insulatethe pivotaliy mounted arcing contact from thecontact arm; The biasing; spring is then electrically connected betweenthe arcing contact and the contact arm so that under arcing conditions,the current is carried at least in part by the spring.

-A magnetic core which is mechanically connected to the arcing contactis then acted upon by the current through this spring which acts as asolenoid winding cit force applied thereto during current conductionthrough the arcing contact.

A stillfurther object of this invention is to insulate an arcing contactfrom the contact arm carrying the arcing contact and electricallyconnecting the arcing contact to the contact arm by circuit means whichwill operate to exert a force upon the arcing contact in opposition tothe blow-oil force applied thereto.

These and other objects of my invention will become apparent from thefollowing description when taken in connection with the drawings inwhich:

FIGURE 1 shows a first embodiment of my novel movable contact armstructure wherein the biasing spring for biasing the arcing contact isused as a solenoid winding under arcing conditions.

FIGURE 2 shows a second embodiment of. my inventi'on. wherein thesolenoid need not act as the main biasing spring for the pivotallymounted contact.

FIGURE 3 is similar to FIGURE 2 and shows the movable contact arm inpartially and fully disengaging position.

FIGURE 4 shows a further embodiment of the invention Where the auxiliaryspring is concentric with the biasing spring.

Referring now to FIGURE 1, a movable contact arm ll of conductivematerial is pivotally mounted on pivot 12. -A main contact 14 is pivotedto arm 10 at pivot The upper end of conto arm that pivot 2d. The pivotalconnection between arm 16 and arcing contact '18 is an insulatedconnection and is formed of a main central pin 22 and an outerinsulating cylinder 24. A relatively stationary contact for cooperatingwith main contact 14 and arcing contact 18 is partially shown asstationary contact member 26 and includes contact surfaces 28 and 31 forcooperating with the main movable contact 14 and arcing contact 18respectively. I I

The arcing contact 18 has a rearwardly projecting portion 30 which ispositioned under an insulated adjustable stop 32 which is formed by athreaded screw member carried by frame 10. The arcing contact 18 is thenbiased toward engagement with stop 32 by a spring 34 which is preferablya beryllium copper spring. The beryllium copper spring is electricallyconnected at its ends between arcing contact 18 and movable contact arm10.

In accordance with the present invention, the relatively movablenon-magnetic member 38 and a magnetic plunger 40 are positioned withinspring 34 and are axially movable therein. Accordingly, when the movablecon tact arm to is moved toward a disengaged position by operating means42, the main movable contact 14 will disengage with respect tostationary contact 28 while the arcing contact 18 will remain engagedwith cooperating contact '31 because of the biasing spring 34 whichbiases the arcing contact toward its engaged position. The current flowwill now form a relatively U-shaped path going through the stationaryarcing contact 31, arcing contact 18, spring 34 land to the main contactarm 10. This U-shaped current path will cause a blowoii action againstarcing contact 18 tending to rotate it in clockwise direction aboutpivot 20 and thus open the circuit before suflicient clearance isachieved between the main movable contact 14 and its cooperating contact28.

The only force counteracting this blow-off force in the past has beenthe biasing spring 34. When, however, the current magnitudes aresufficiently high, this spring force will be overcome prematurely.

In accordance with the present invention, when the main contact 14disengages, the arcing current flows through spring 34 so that thespring acts as a solenoid winding. Accordingly, the plunger 40 ofmagnetic material will be drawn upwardly with a strong force intoengagement with member 38 which, in turn, engages the rearwardlyprojecting portion 3a of the arcing contact to drive it in acounter-clockwise direction and against the blow-off force.

FIGURE 2 shows a second embodiment of my novel invention whereinnumerals similar to those used in FIGURE 1 identify similar components.The embodiment of FIGURE 2 diifers from the embodiment of FIGURE 1 inhaving the auxiliary blow-off force means independent of the biasingspring 34 of FIGURE 1 so that the material used for the biasing springmay be selected to have the best spring properties. In FIGURE 2, biasingspring 34 is not shown in order to simplify the drawings, but is presentand operates in the same manner as described in FIGURE 1 with theexception of the electrical action.

FIGURE 2 shows a projecting arm 44 which is directly connected to arcingcontact 18 to be rotatable therewith. The end of arm 44 is terminated bya magnetic button 46. Magnetic button 46 is positioned adjacent an ironcore 48 and separated therefrom by an air gap and core 48 is rigidlyconnected to contact arm 10. A spring member or coil 50 which is of amaterial having good electrical conducting characteristics has one end52 mechanically and electrically connected to arcing contact 18 and itsother end 54 mechanically and electrically connected to contact arm 10.The spring 50 surrounds magnetic core 40 and button 46.

In the structure of FIGURE 2, when the movable contact arm is operatedto move toward a disengaged position and after a disengagement of themain movable contact 14, a current flow is established through spring 50as seen from the solid line position in FIGURE 3. This establishes amagnetic'field within the spring so that magnetic button 46 is attractedtoward core 48 to exert a counter-clockwise force on arcing contact 18about pivot 20 which, along with the biasing force of the normal biasingspring acting on arcing contact 18, will counteract the blow-01f forceimparted to contact 18.

As seen in the solid line position of FIGURE 3, the arcing contact 18will remain in engagement with contact 31 in which movable contact 14has established a sufiicient clearance distance from main stationarycontact 28. After this distance has been reached, the continued motionof contact arm 10 to its fully disengaged position shown in the dot-dashview of FIGURE 3 will move the arcing contact 18 away from contact 31and against stop 32. which picks-up rearwardly projecting end 30 ofarcing contact 18.

A further embodiment of the auxiliary spring solenoid means of FIGURES 2and 3 is shown in FIGURE 4 where the auxiliary conducting spring 56 isconcentrically positioned with respect to the main biasing spring 58which is similar to biasing spring 34 of FIGURE 1.

In FIGURE 4, the main biasing spring 58 is seated upon an insulated base60 carried by contact arm it] and conductive spring or coil 56 which iselectrically connected to arcing contact 18 at end 62 and to movablecontact arm 10 at end 64 is concentrically positioned with respect tomain spring 58. As was the case of FIGURE 1, a magnetic plunger 66 whichis axially movable within spring 56 serves as the solenoid plunger forthe solenoid winding formed by spring 56.

Accordingly, when current is established through the arcing contact,this current flows from arcing contact 18 through spring 56 to contactarm 19 to establish a magnetic field which will drive plunger 66upwardly. This will force plunger 68 into engagement with rearwardiyextending portion 30 of arcing contact 18 to thereby drive it in acounterclockwise direction and reinforce the biasing force of mainbiasing spring 58.

In the foregoing, I have described my invention only in connection withpreferred embodiments thereof. Many variations and modifications of theprinciples of my invention within the scope of the description hereinare obvious. Accordingly, I prefer to be bound not by the specificdisclosure herein but only by the appending claims.

I claim:

1. A movable contact arm for a circuit breaker; said movable contact armbeing movable between an engaged and disengaged position with respect toa cooperating contact; said movable contact arm carrying a main contactand an arcing contact; said arcing contact being pivotally connected tosaid contact arm; abutting means mounted to said movable arm forlimiting the motion of said arcing contact with respect to said contactarm; said arcing contact being electrically insulated from said contactarm at the pivot point; a biasing means for normally biasing said arcingcontact towards an engaged position with respect to said cooperatingcontact; an auxiliary means for imparting additional force to saidarcing contact in the direction of the force imparted by said biasingmeans; said auxiliary means electrically connecting said arcing contactto said contact arm for generating a magnetic field; said auxiliarymeans including a magnetic means movable against and imparting a forceto said arcing contact responsive to said magnetic field.

2. A movable contact arm for a circuit breaker; said movable contact armbeing movable between an engaged and disengaged position with respect toa cooperating contact; said movable contact arm carrying a main contactand an arcing contact; said arcing contact being pivotally connected tosaid contact arm; abutting means mounted to said movable arm forlimiting the motion of said arcing contact with respect to said contactarm; said arcing contact being electrically insulated from said contactarm at the pivot point; a biasing means for normally biasing said arcingcontact toward an engaged position with respect to said cooperatingcontact; said biasing means including a. high conductivity springelectrically connecting said arcing contact to said contact arm; saidspring having a magnetic member contained therein; said magnetic memberbeing movable toward said arcing contact to impart a force to saidarcing contact in the same direction as the biasing force of said springresponsive to current flow therethrough.

3. A movable contact arm for a circuit breaker; said movable contact armbeing movable between an engaged and disengaged position with respect toa cooperating contact; said movable contact arm carrying a main contactand an arcing contact; said arcing contact being pivotally connected tosaid contact arm; abutting means mounted to said movable arm forlimiting the motion of said arcing contact with respect to said contactarm; said arcing contact being electrically insulated from said contactarm at the pivot point; a biasing means for normally biasing said arcingcontact towards an engaged position with respect to said cooperatingcontact; an auxiliary means including a solenoid Winding connecting saidarcing contact to said contact arm, and a magnetic member within saidsolenoid; said magnetic member being movable toward said arcing contactto impart a force to said arcing contact in the same direction as thebiasing force of said biasing means responsive to current flow throughsaid arcing contact.

4. A movable contact arm for a circuitbreaker; said movable contact armbeing movable between an engaged and disengaged position with respect toa cooperating contact; said movable contact arm carrying a main contactand an arcing contact; said arcing contact being pivotally connected tosaid contact arm; abutting means mounted to said movable arm forlimiting the motion of said arcing contact with respect to said contactarm; said arcing contact being electrically insulated from said contactarm at the pivot point; a biasing means for normally biasing said arcingcontact towards an engaged position with respect to said cooperatingcontact; an auxiliar y means including a solenoid winding connectingsaid arcing contact to said contact arm, and a magnetic member withinsaid solenoid; said magnetic member being movable toward said arcingcontact to impart a force to said arcing contact in the same directionas the biasing force of said biasing means responsive to current flowthrough said arcing contact; said biasing means being a spring. 1

5. A movable contact arm for a circuit breaker; said movable contact armbeing movable between an engaged and disengaged position with respect toa cooperating contact; said movable contact arm carrying a main contactand an arcing contact; said arcing contact being pivotaily mounted withrespect to said contact arm; said arcing contact being electricallyinsulated from said contact arm at the pivot point; 'a biasing means fornormally biasing said arcing contact towards an engaged position withrespect to said cooperating contact; said biasing means including a highconductivity spring electrically connecting said arcing contact to saidcontact arm; said spring having a magnetic member contained therein;said magnetic member being movable toward said arcing contact to imparta force to said arcing contact in the same direction as the biasingforce of said spring responsive to current flow therethrough.

6. A movable contact arm for a circuit breaker; said movable contact armbeing movable between an engaged and disengaged position with respect toa cooperating contact; said movable contact arm carrying a main contactand an arcing contact; said arcing contact being pivotally mounted withrespect to said contact arm;

said arcing contact being electrically insulated from said contact armat the pivot point; a biasing means for normally biasing said arcingcontact towards an engaged position with respect to said cooperatingcontact; an auxiliary means including a solenoid winding connecting saidarcing contact to said contact arm, and a magnetic member within saidsolenoid; said magnetic memher being movable toward said arcing contactto impart a force to said arcing contact in the same direction as thebiasing force of said biasing means responsive to current flow throughsaid arcing contact; said biasing means being a spring.

7. A contact for a circuit breaker; said contact being pivotally mountedon a movable contact arm; a biasing spring for biasing said contact in afirst direction; and auxiliary means for imparting additionaliorce tosaid contact to move said contact in said first direction; saidauxiliary means electrically connecting said contact to said contact armand being operable responsive to current flow through said movablecontact; said auxiliary operating means including a solenoid meanswinding conducting the current through said contact and a plungermovable toward engagement with said contact when said solenoid windingis energized.

8. A contact for a circuit breaker; said contact being pivotally mountedon a movable contact arm; a biasing spring for biasing said contact in afirst direction; and auxiliary means for imparting additional force tosaid contact to move said contact in said first direction; saidauxiliary means electrically connecting said contact to 7 ReferencesCited in the file of this patent UNITED STATES PATENTS 1,762,604Ainsworth June 10, 1930 1,804,628 MacNeill May 12, 1931 1,827,430Greenwood Oct. 13, 1931 2,186,251 Lindstrom Jan. 9, 1940 2,761,040Ulrich Aug. 28, 1956

